New binders for high-solids coatings

Two-component polyurethane coatings with a high solids content emit only low amounts of volatile organic compounds, thus satisfying the requirements of the VOC directives. Bayer MaterialScience now offers two new binders for high-solids coatings: Desmophen

Desmophen® A XP 2594 is an environmentally friendly raw material tailored for the formulation of automotive refinishing coatings. It is used for the formulation of coatings which dry significantly faster than those formulated with a first generation binder – a real productivity advantage. The cured coating films are also substantially more resistant to gasoline, brake fluid and other chemicals.

“High-solids automotive refinishing coatings have now reached the property level of established systems having a 15 percent lower solids content and thus containing more solvent,” says Holger Mundstock, an expert on polyurethane automotive refinishing coatings at Bayer MaterialScience.

The development team at Bayer MaterialScience achieved this advancement by means of a polyacrylate with a high content of crosslinking sites, i.e. an especially large number of hydroxyl groups. The high-grade monomers used in Desmophen® A XP 2594 are an additional factor behind the excellent film properties. These include very good weather stability and high UV resistance. The new binder enables the formula­tion of clearcoats or solid color topcoats with a VOC content of less than 420 g/L.

The fact that Desmophen® A XP 2598 only requires a small amount of hardener for crosslinking due to its low content of free hydroxyl groups has a positive effect on price. The coatings can be used for the coating of e.g. agricultural machinery.
The second high-solids acrylate is intended for applications with a less demanding requirement profile than automotive refinishing.

According to Dr. Ulrich Freudenberg, an expert on polyurethane industrial coatings at Bayer MaterialScience, “Desmophen® A XP 2958 is the perfect binder for cost-effective, low-VOC coatings for metal industrial goods.” These include a broad spectrum of products, from heating elements and household appliances, through shock absorbers and other automobile parts, to machine tools and agricultural and construction machinery. The monomers have been carefully selected to permit a relatively low binder price. Also having a positive effect on price is the fact that Desmophen® A XP 2598 only requires a small amount of hardener for crosslinking due to its low content of free hydroxyl groups.

As with Desmophen® A XP 2594, coatings formulated with the new polyacrylate are very quickly assembly-ready, further enhancing its economy. Gloss, adhesion and weather stability of the resulting coatings are all as expected of a good industrial coating.

Both new binders can be combined with almost any aliphatic hardener in the Desmodur® N range.